Pump



Nov. 11, 1930. A, CNAB 1,781,404l

PUMP

Filed Sept. 3, 1929 y M @i 9 .Patented Nov. ll, 1930 ALEXANDER MONI'AB, OF BBIDGEPORT, CONNECTICUT PUMP Application led September 3, 1929. Serial No. 390,187.

' This invention relates to a new or improved pump for use either in compressing li uids or gases, or for use in transferring liqui s or gases from one location to another, or for use in e'ecting a vacuum, or reduction of pressure.

A primary object of the present invention is to provide an improved pump that can be operated with eciency when pumping fluids io subjected to comparatively wide ranges ofv temperature, or which can be alternately used for attaining a high degree of vacuum and for pumping under comparatively great pressure. y

A further object of the present invention is to provide such a pump in which the volume of fluid delivered is varied to compensate for the changes in the pressure at which the pump is operated, in order to maintain the load on the pump driving mechanism more constant and to avoid the necessity for comparatively wide changes in the speed at which the pump is operated. 11

A further object of the present invention is to provide for such compensation in the delivery effected by the pump by means of changes in the effective piston area of the pump and further to e'ect such changes automatically as the pressure conditions under which the pump is operating vary.

A further object of the present invention is to obtain the above objects by means of a sim le and rugged construction that can be rea ily manufactured at low cost and which involves a minimum number of moving parts that can be readily assembled. A further object of the present invention is to provide such a pump which can be constructed in a light form, and which will operate under varying conditions with absolute certainty over long periods and with a minimum of attention.

While it will be appreciated from the foregoing remarks that the present invention is 45 applicable to a wide lie d of use, the present invention has been developed more par` ticularly for use in pumping li uid to eiect hydraulic operations, and a pre erred exam- ..S ple of the invention which is-applicable to the raising and lowering of the landing gear of amphibian aircraft will now be described with reference to the accompanying drawings, in which JFigure l is a longitudinal section of the pump on the line 1-1 of Figure 2; e5

Figure 2 is a transverse section on the line 2--2 of Figure 1.

As illustrated, the pump comprises a body member 10 which forms a major working cylinder. The interior of body member 10 has eo its upper end of slightly greater diameter than its lower end, with a shoulder 1l formed at the junction of the two interior diameters.

A cylinder head member l5 has a screwthreaded engagement at the other end of e5 body member 10, and said head member has an inlet port 16 and an outlet port 17, each of which communicates with a transversely located passage 18, respectively, by way of an inlet valve 19fand an outlet valve 20, valves 70 19 and 20 being spring pressed into engagement with valve seats formed in the passage 18. Intermediately of the valves 19' and 20 the passage 18 has an opening 21 which communicates with the interior of the body member 10. The head member is also provided with a second transverse` passage 25 Afor establishing communication between the outlet port 17 and the inlet port 16, this passage 25 serving as a bye-pass passage and so being normally closed by a valve 26 which is urged into engagement with its seat by means of a comparatively strong spring 27. The valve 26 is mounted independently for sliding movement in the passage 25 and is 85 engaged centrally by an independently mounted sliding rod 28 which carries a collar 29 engaged at one end by the spring 27, the other end of spring 27 being in engagement with an adjustable abutment 30.

The lower end of body member 10 has a screw-threaded engagement with a closure member 35 which is provided axially with an extended aperture 36 for bearing engage ment with a piston rod 37.

A major piston 40 comprises a tubular member having an external shoulder'portion 41 intermediate its ends, this shoulder por tion 41 being in sliding engagement with the large diameter of the interior of body 100 member and adapted to abut against the shoulder 11. The upper end of tubular inem-` ber 40 is provided with a packing jointv which inc-ludes ring members 42 of U-shaped cross-section, these ring members being retained in position between shoulder member 41 and the ring 43 which has a screwthreaded engagement with the up er extremity of the piston member 40. he exterior periphery of ring member 43 is in sliding engagement with the interiorof body member 10 and has, longitudinal grooves 44 for permitting the access of pressure to the upper ring member 42. The shoulder member 41 and ring 43 with the packing therebetween thus form a large upper endto the major piston 40. At-the lower end of the major piston there is provided an internal shoulder having an axial opening through which the piston rod 37 loosely extends. rlhe end of iston rod 37 is provided with a minor piston 51. The minor piston 51 com- -prises a body member 52, packing members 53 of L-shaped cross-section separated by a ring 54, and a cover ring 55, all secured on' a reduced end 56 of piston rod 37 by means fof a nut 57. The minor piston 51 thus has a fluid-tight. sliding engagement with the cylindrical interior of the major piston 40, said cylindrical interior forming a minor cylinder.

Disposed between the lower end of the minor piston 40 and the closure member 35 n is a floating tubular member 60 which has an internal shoulder 61 at its upper end and an external shoulder 6 2 atits lower end. A

i coiled compression spring 63 is disposed fil within tubular member 60 and has one end in abutting engagementwith shoulder 61 and its other end in abutting engagement with the closure memberl 35. A second coiled compression spring v65 has one end in abutting-en agement with the shoulder portion "41- of t e minor .piston 40 and its other end in abutting engagement with the shoul- -der 62 ofJ the tubular'member 60.

In operation the pump is driven by a mechanism which eifects the reciprocation ofthe piston 'rod 37. The minor piston 51 at all times reciprocates as a unit with the reciprocations ofthe piston rod 37, and inv advance lmovement of the piston rod from retracted position shown in Figure 1 the major piston 40 will be caused to move asaiinit with the minor piston 51 bythe action of the springs 6 3 and 65 so long as the pressure developedv is insufficient to `overcome the action of the s rings. A comparatively large volume of uid will thusbe displaced with each stroke lof the combined piston. Assoon, however,

as the pressure will have been built up toa degree suicient to maintain lthe shoulder 41 of the major piston in engagement` withthe shoulder 11 of the body member 10and there'- after the minor piston 51 only will .reciprocate, thus delivering a comparatively small volume of fluid under high pressure without unduly increasing the load imposed onthe driving mechanism. When the pressure-in `thesystem has risen suiciently the by-pas's ivalve- 26 will open and iiuid will thereafter circulate through the passage 25until the operationv of the pumpL driving mechanism is- 2. A pump comprising, in combination, a

major cylinder and a major piston operative therein; spring means within said cylinder abutting one end thereof and engaging one side of said piston for advancing same towards the other end of said major cylinder; a minor piston operative within a minor cylinder formed insaid major piston; means for reciprocating said minor piston; co-engaging faces in said minor iston and major piston for causing said maJor piston to follow the movement of the minor piston in the retractive movement of the latter; said spring means being of 'limited strength in relation to the maximum iluid pressure to be operated on; and'co-engaging stop faces on said major cylinder and major piston for limiting the retractive movement of said major piston.

3. A pump comprising, in combination, a

aving a minor cylinder open at one end e a minor pismajor cylinder; anda major piston operative therein; spring means within said cylinder abutting one end thereof and engaging one side of said piston for advancing same towards the other end of said major cylinder; a minor piston operative within a minor c linder formed in said major piston; means gbr reciprocatin said minor piston; coengaging faces in sai minorpiston and maJor piston for causing said maJor piston tov follow the movement of the minor piston in the retrac tive movement of the latter; and co-engaging' stop Afaces on said major cylinder and major .piston for limitingthe retractive movement of s aid major piston; said minorv cylinder having one end vat all times in communication` vwith, said' major cylinder.

In Atestlmony whereof I ax my signature hereto.

' ALExANDEi'i MONAB. 

